RESUMO
Cylindrical re-entrant cavities are unique three-dimensional structures that resonate with their electric and magnetic fields in separate parts of the cavity. To further understand these devices, we undertake rigorous analysis of the properties of the resonance using "in-house" developed Finite Element Method (FEM) software capable of dealing with small gap structures of extreme aspect ratio. Comparisons between the FEM method and experiments are consistent and we illustrate where predictions using established lumped element models work well and where they are limited. With the aid of the modeling we design a highly tunable cavity that can be tuned from 2 GHz to 22 GHz just by inserting a post into a fixed dimensioned cylindrical cavity. We show this is possible, as the mode structure transforms from a re-entrant mode during the tuning process to a standard cylindrical transverse magnetic mode.
RESUMO
The prairie vole (Microtus ochrogaster) has recently been shown to be glucocorticoid resistant; that is, the prairie vole adrenal axis is refractory to dexamethasone challenge, and highly elevated basal corticosterone titers occur without apparent pathophysiology. This study investigates the physiological correlates of glucocorticoid resistance in the prairie vole. We provide a detailed pharmacological characterization of intracellular type I and type II adrenal steroid receptors in peripheral tissues and the hippocampus of the prairie vole and the Sprague Dawley rat, a corticosensitive rodent. Adrenalectomy markedly reduces, but does not eliminate, circulating glucocorticoids in the prairie vole. Nonetheless, molecular, cellular, and physiological assays indicate adrenal insufficiency; salt appetite and dentate gyrus granule cell death are increased after adrenalectomy, suggesting vacancy of the high affinity type I subtype of central adrenal steroid receptor. Analysis of adrenal steroid receptor binding constants and selectivity for endogenous and synthetic steroids in the vole and rat indicated that the vole type I receptor is nearly identical to that of the rat in brain and periphery. However, voles demonstrated a 2-fold lower type I receptor binding density in colon and hippocampus compared with that in rats. The vole type II receptor bound the endogenous glucocorticoid corticosterone with an 8- to 10-fold lower affinity than the rat type II receptor and was expressed in lower densities in thymus and hippocampus. These data indicate physiological adaptations in the prairie vole adrenal axis consistent with other glucocorticoid-resistant species, such as the guinea pig and squirrel monkey.
